The present invention relates to a recording medium recording digital information thereon, a recording medium functioning as a nonvolatile memory, an information reproducing apparatus, an information recording apparatus, and an information recording and reproducing apparatus using the same.
Conventionally, as a ROM (read only memory) recording medium of digital information and an information reproducing apparatus thereof, there are a CD (compact disk) and a player of the same.
FIG. 28 is a block diagram schematically showing that apparatus.
In FIG. 28, reference numeral 100 is a CD and reference numeral 200 is a player.
In the CD 100, pits 102 are formed as digital information in a signal layer 101. A protective layer 103 and a transparent plastic substrate 104 are adhered to an upper surface and a lower surface of this signal layer 101.
In such a CD 100, the track pitch is set to 1.6 xcexcm and the shortest pit length is set to 0.9 xcexcm.
The player 200 is an apparatus which detects the existence of the pits 102 to reproduce the information of the CD 100 and is provided with an optical pick-up 201, an RF amplifier 202, a digital signal processing circuit 203, etc.
Namely, a laser beam L having a wavelength of 780 nm is fired from a laser diode 210 of the optical pick-up 201 to the CD 100 side. The reflected laser beam L is detected at the photodiode 211. The RF signal is amplified by the RF amplifier 202, then subjected to digital processing etc. at the digital signal processing circuit 203 to reproduce the information of the CD 100.
The CD 100 and the player 200 thereof described above, however, are structured to use a laser beam L to optically detect the pits 102 of the CD 100, therefore there is a limit to the wavelength of that beam and the precision of detection is low. For this reason, the size of the pits 102 cannot be made small and a large amount of information cannot be recorded on the CD 100. For example, in a CD 100 having a diameter of 12 cm, the recordable amount of digital information is about 650 megabytes.
Further, as other recording media and the information reproducing apparatuses thereof, there are the recently much talked about DVD (digital video disk) and the players thereof.
In this apparatus, the track pitch of the DVD is set to 0.84 xcexcm and the shortest pit length is set to 0.451 xcexcm, so the existence of the pits can be detected by a laser beam having a wavelength of 635 nm or less. Accordingly, a higher density and larger amount of information can be recorded on a DVD in comparison with the CD 100. Nevertheless, the amount of digital information which can be recorded on a DVD of a diameter of 12 cm is about 3.9 gigabytes.
Contrary to this, when the information of the CD and DVD is detected by using a laser beam having a blue wavelength, the precision of detection is improved. However, since the pits are detected by using light, there is a limit and thus only information of a magnitude of 0.45 xcexcm to 0.3 xcexcm at the lowest can be detected.
Accordingly, the conventional recording media such as CDs and DVDs and the information reproducing apparatuses using the same were insufficient as multimedia apparatuses, for which recording and reproduction of a large amount of information such as moving picture information and audio information were required.
On the other hand, as a recording medium which can be recorded on and reproduced from like a nonvolatile memory of a semiconductor and an information recording and reproducing apparatus thereof, there are a so-called xe2x80x9cMini Discxe2x80x9d and a player thereof.
The xe2x80x9cMini Discxe2x80x9d recording medium is a magneto-optic disk 300 as shown in FIG. 29 and is structured with a magnetic layer 302 formed on a polycarbonate substrate 301 in a corrugated manner and with a protective layer 303 provided on the magnetic layer 302.
When recording, the laser beam strikes the recording medium and heats the same while an external magnetic field is applied, the magnetization is inverted and information of xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d is recorded according to the orientation of the domain. Then, when reproducing, using the fact that the plane of polarization of the reflected light of the laser beam slightly rotates in a forward or reverse direction corresponding to the orientation of the magnetization of the magnetic layer (Kerr effect), the laser is irradiated, a laser beam is fired to read the orientation of the magnetization.
In the xe2x80x9cMini Discxe2x80x9d as well, however, since light is used for the sensing medium, it is not possible to exceed the limit of the wavelength of light. As shown in FIG. 29, the pitch of the recording width is 1.1 xcexcm+0.5 xcexcm, i.e., about 1.6 xcexcm.
The present invention was made so as to solve the above problem and has as an object thereof to provide a ROM recording medium and a recording medium functioning as a nonvolatile memory enabling an increase of the capacity of the information and an improvement of the precision of the reading of the information and an information reproducing apparatus, an information recording apparatus, and an information recording and reproducing apparatus using the same.
According to the present invention, to achieve the above object, as a first aspect of the invention, the recording medium disclosed in claim 1 is configured provided with a substrate, a signal layer made of a metal which is fixed to the surface of the substrate, and pits formed in the same.
The recording medium disclosed in claim 1 is structured as the invention disclosed in claim 2 provided with a protective plate which covers the signal layer and is stuck to the surface of the signal layer by the state of vacuum in the pits.
The invention is configured as the recording medium with the signal layer formed by aluminum or another flexible metal conductor.
As a second aspect of the present invention, the information reproducing apparatus disclosed in claim 4 is configured provided with an electron gun which can fire an electron beam at predetermined positions of a metal medium having a signal layer made of metal in which pits are formed, a detector which can detect an intensity of the electron beam reflected from the signal layer of the recording medium, and a reproducing circuit which reproduces the information of the recording medium based on the result of detection of the detector.
Further, as a third aspect of the present invention, an information reproducing apparatus disclosed in claim 5 is configured provided with a metal body which can be arranged so as to face the signal layer at predetermined positions of a recording medium to which a predetermined voltage is applied and having a signal layer made of metal in which pits are formed, a detecting circuit which can detect the existence of a change of a potential between the metal body and the signal layer, and a reproducing circuit which reproduces the information of the recording medium based on the result of detection of the detecting circuit.
As a fourth aspect of the present invention, the recording medium disclosed in claim 6 wherein provision is made of island-like fixed electrodes electrically insulated from the periphery, electrons can be injected into the fixed electrodes by the electron gun, and injected electrons can be removed, thereby imparting a memory function to the fixed electrodes.
The recording medium disclosed in claim 7 is configured as a recording medium disclosed in claim 6 provided with a substrate, a conductive layer laminated on the substrate surface, an insulating layer laminated on the conductive layer, and island-like fixed electrodes embedded in the insulating layer.
As a fifth aspect of the present invention, the information recording apparatus of the recording medium disclosed in claim 8 is configured provided with an electron gun which injects electrons in fixed electrodes of a recording medium provided with island-like fixed electrodes electrically insulated from the periphery via the insulating layer in the conductive layer.
The information recording apparatus disclosed in claim 9 is configured as the information reproducing apparatus disclosed in claim 8 further provided with an apparatus applying a predetermined voltage to the conductive layer of the recording medium and having a function enabling the information of the recording medium to be erased all together by applying a predetermined voltage to the conductive layer.
As a sixth aspect of the present invention, an information reproducing apparatus of the recording medium disclosed in claim 10 is configured provided with a counter electrode which can be arranged opposite to the fixed electrode of the recording medium in which island-like fixed electrodes electrically insulated from the periphery via an insulating layer are provided in a conductive layer, a detector which can detect the change of an electrostatic capacitance between a fixed electrode and a counter electrode, and a reproducing circuit for reproducing the information of the recording medium based on the result of detection of the detector.
As a seventh aspect of the present invention, an information recording and reproducing apparatus disclosed in claim 11 is configured provided with both of the information recording apparatus disclosed in claim 8 and the information reproducing apparatus disclosed in claim 10.
The recording medium of the present invention is a recording medium which uses electrons as the sensing medium and can record a larger volume of information by using electrons in place of light similar to an electron microscope with which a finer pattern can be enlarged and viewed than with an optical microscope.
According to the recording medium according to the first aspect of the invention, a signal layer made of metal is used, therefore by emitting an electron beam to predetermined positions of this signal layer and detecting the electron beam reflected from the same, the information of the recording medium can be read. In this signal layer, pits can be easily formed by pressing etc.
Further, when a protective plate is provided covering the signal layer of the recording medium, dust or the like will not enter into the pits etc. at the time of storage. When this protective plate is peeled off, the signal layer made of metal in which the pits are formed is exposed.
Further, by forming the signal layer by an aluminum or other flexible metal conductor, the pits of the signal layer can be formed further easily with a higher precision.
Further, according to the information reproducing apparatus according to the second aspect of the invention, the electron beam emitted from the electron gun is reflected at a predetermined position of the signal layer. At this time, where there is a pit at the predetermined position, the electron beam is scattered and a weak electron beam is detected by the detector. Further, when there is no pit at the predetermined position, the electron beam is reflected at the detector side and a strong electron beam is detected by the detector. Then, based on the result of the detection, the information of the recording medium is reproduced at the reproducing circuit.
Further, according to the information reproducing apparatus according to the third aspect of the invention, if the signal layer of the recording medium and the metal body are brought into very close contact with each other, when there is no pit at a predetermined position of the signal layer, a discharge occurs between the signal layer and the metal body. Accordingly, when the metal body moves from a position where there is a pit to a position where there is no pit, a large change in potential occurs between the metal body and the signal layer and the existence of the change is detected by the detecting circuit. Then, based on the result of the detection, the information of the recording medium is reproduced by the reproducing circuit.
Further, when the signal layer of the recording medium and metal body are not brought into close contact with each other, the signal layer and the metal body do not cause a discharge and act as a capacitor. Accordingly, when the metal body moves from a position where there is a pit to a position where there is no pit, a change occurs in the capacitor potential between the metal body and the signal layer and the existence of the change is detected by the detecting circuit. Then, based on the result of the detection, the information of the recording medium is reproduced by the reproducing circuit.
In the recording medium according to the fourth aspect of the invention, island-like fixed electrodes electrically insulated from the periphery are provided embedded in for example the insulating layer. xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d can be recorded according to whether electrons are injected or not injected into the fixed electrodes by the electron gun. When a conductive layer is provided beneath the fixed electrodes, the electrons which do not reach the fixed electrodes are absorbed into the conductive layer beneath them and the charging of electrons of the insulating layer can be avoided. The electrons injected into the fixed electrodes are not discharged since the fixed electrodes are insulated from the periphery, thus there is a nonvolatile memory function. In this case, there is no change in the physical properties, therefore there is no limit in the number of times of writing. For the discharge of the injected electrons, if a voltage is applied to for example the conductive layer of the recording medium, electrons stored in the electrodes can be attracted by and absorbed into the conductive layer, whereby the information can be erased all together like the flash memory of a semiconductor memory.
Further, in the information recording apparatus according to the fifth invention, information can be recorded by injecting electrons into the fixed electrodes of the recording medium by the electron gun.
Before recording the information on the recording medium, in order to discharge the injected electrons so as to erase the information all together, if a function of applying a voltage to the conductive layer of the recording medium is imparted to the information recording apparatus, electrons stored in the electrodes can be absorbed into the conductive layer, whereby the information can be erased all together like the flash memory of a semiconductor memory.
In the information reproducing apparatus of the sixth aspect of the invention, when a counter electrode is placed close to a fixed electrode and the counter electrode comes into close contact with a fixed electrode into which electrons have been injected due to a proximity effect (capacitance bond), a large electrostatic capacitance is caused. When it comes into close contact with a fixed electrode into which electrons have not been injected, a small electrostatic capacitance is caused, therefore when the fixed electrode is scanned by this counter electrode, a change of electrostatic capacitance between the fixed electrode and the counter electrode occurs, this is detected by the detector, thus the information recorded on the recording medium can be reproduced based on the result of the detection of this detector.
In the information recording and reproducing apparatus of the seventh aspect of the present invention, by providing both of the information recording apparatus and the information reproducing apparatus, the recording and reproduction become possible by one apparatus, thus the apparatus becomes compact.